1. Field of the Invention
The present invention relates to a substrate processing apparatus which comprises a plurality of processing portions.
2. Description of the Background Art
A substrate processing apparatus is used to apply various types of processing to a substrate such as a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for photomask and a glass substrate for optical disk. During processes for manufacturing of a semiconductor device, for example, to enhance the efficiency of the production, a substrate processing apparatus is used which integrates a plurality of processing units each performs each type of a series of processing. In general, such a substrate processing apparatus is connected to power supply equipment (external power source), so that electric power which is supplied from the power supply equipment drives the plurality of processing units.
FIG. 9 is a block diagram showing an electric power system in a conventional substrate processing apparatus. In FIG. 9, a substrate processing apparatus la comprises a plurality of processing units 11, 12, 13 and 14 each for applying predetermined processing to a substrate. Power receiving parts of the plurality of processing units 11, 12, 13 and 14 are connected to an external power source E through a turn-on switch 30 and a breaker 20. As the turn-on switch 30 is turned on, electric power from the external power source E is supplied to the plurality of processing units 11, 12, 13 and 14.
Resistor elements such as a filament of a lamp and a nichrome wire of a heater are used in the respective processing units 11, 12, 13 and 14. When such a resistor element carries a current, although a large amount of heat is developed, the lower the temperature of the resistor element is, the smaller an electric resistance of the resistor element is. At turn-on, the temperature of the resistor element is low. The temperature increases with time, and stabilizes at a certain temperature. Hence, immediately after turn-on, a larger current flows than in a steady state.
FIG. 10 is a view showing a change with time in electric power which is used by the substrate processing apparatus 1a of FIG. 9. Since electric power is supplied simultaneously to the plurality of processing units 11, 12, 13 and 14 upon turn-on in the substrate processing apparatus 1a of FIG. 9, due to the electric behavior described above of each one of the processing units 11, 12, 13 and 14, as shown in FIG. 10, used electric power which is used by the substrate processing apparatus 1a as a whole is large during a certain period of time from a turn-on time t0, but drops lower than a certain constant level Wd once the substrate processing apparatus 1a enters a steady state. In this case, it is necessary to set a working level Wa of the breaker 20 larger than the used electric power of immediately after turn-on, so that a power supplying capability of the external power source E is larger than the working level Wa of the breaker 20.
However, to increase the power supplying capability of the external power source E is not preferable for safety, and also requires a large scale of facilities and leads to an increase in a maintenance cost. This forces a great burden on a user of the substrate processing apparatus 1a.
Further, in a substrate processing apparatus which comprises a plurality of heating units (hot plates) among processing units, a temperature adjusting controller is disposed which adjusts a processing temperature within each heating unit. The heating units each comprise a substrate supporting plate for supporting a substrate and a heater for heating the substrate supporting plate. Processing temperatures for the respective heating units are set as target temperatures in the temperature adjusting controller.
At turn-on, the temperature adjusting controller supplies electric power from an external power source to the heaters of the respective heating units and heats the substrate supporting plates. Once the temperature of the substrate supporting plate of each heating unit reaches a target temperature, in order to keep the temperature of the substrate supporting plate at the target temperature, the temperature adjusting controller ON/OFF controls a current which is supplied to the heater of the heating unit.
Hence, used electric power which is by the substrate processing apparatus 1a as a whole is high during a period of time from turn-on until adjustment of the temperatures of the respective heating units completes, and the used electric power is low during heat retaining after the adjustment of the temperatures of the respective heating units completes
In addition, when a recipe (i.e., procedures) is changed in response to a change in a lot which contains a substrate which is to be processed, the target temperatures for the respective heating units which are set in the temperature adjusting controller are also changed.
In this case, the temperature adjusting controller supplies the electric power from the external power source to the heaters of the respective heating units until the temperatures of the substrate supporting plates of the respective heating units reach the changed target temperatures. After the adjustment of the temperatures of the respective heating units completes, to keep the temperatures of the substrate supporting plates of the respective heating units at the target temperatures, the temperature adjusting controller ON/OFF controls the current which is supplied to the heaters of the respective heating units.
Hence, used electric power which is used by the substrate processing apparatus 1a as a whole is high during the adjustment of the temperatures of the respective heating units after the target temperatures are changed, and the used electric power is low during heat retaining after the adjustment of the temperatures of the respective heating units completes.
In this case, during the period of time from turn-on until the adjustment of the temperatures of the respective heating units completes and during the period from the change in the target temperatures until the adjustment of the temperatures of the respective heating units completes, the external power source is demanded to have a power supplying capability which is larger than the electric power used after the adjustment of the temperatures, and wire material parts of the electric power system are demanded to have capacities which correspond to the used electric power. This makes energy conservation and cost reduction difficult.